TrustedVolumes $6.7M Loss: Unguarded Signer Allowlist in 1inch RFQ Proxy — Same Attacker as 2025 Fusion V1 Hack

In May 2026, TrustedVolumes — a 1inch ecosystem market maker — lost $6.7M after an attacker exploited a public, entirely unguarded function that let any address register itself as an authorized order signer in the protocol's RFQ swap proxy. Behavioral analysis links the attacker to the March 2025 1inch Fusion V1 exploit.

Root Cause

TrustedVolumes' custom Request-for-Quote (RFQ) swap proxy contract exposed a signer-registration function with no access control modifier. Any external account could call the function, self-register as an allowed signer, then submit fraudulent swap orders that the contract accepted as legitimate — because signature recovery returned an address on the allowlist.

// Pseudocode illustrating the vulnerable allowlist function
contract RFQSwapProxy {
    mapping(address => bool) public allowedSigners;

    // BUG: No onlyOwner, no role check, no gate whatsoever
    function addSigner(address signer) external {
        allowedSigners[signer] = true;
    }

    function executeOrder(
        Order calldata order,
        bytes calldata sig
    ) external {
        address recovered = ECDSA.recover(orderHash(order), sig);
        require(allowedSigners[recovered], "Unauthorized signer");
        // Transfers assets to order.recipient — controlled by attacker
        _settle(order);
    }
}

The fix is trivial — add onlyOwner or an AccessControl role guard to addSigner. The absence of this guard turned the entire protocol's asset custody into an open withdrawal function.

Attack Steps

Step	Detail
1	Attacker calls `addSigner(attackerEOA)` — no revert, no authorization check
2	Attacker signs fraudulent `Order` structs directing all major token balances to attacker wallets
3	Attacker calls `executeOrder()` — signature check passes (recovered address is now "allowed")
4	~$6.7M in WETH, WBTC, USDT, USDC transferred out across multiple transactions
5	Stolen tokens swapped for ETH on DEX; proceeds split across three attacker-controlled addresses

Attribution note (unconfirmed): Verichains' behavioral analysis of on-chain patterns suggests the same threat actor was responsible for the March 2025 1inch Fusion V1 exploit, bringing total attributed losses from this actor across two separate RFQ-architecture attacks to over $11M.

Impact

Total drained: ~$6,700,000 (WETH, WBTC, USDT, USDC)
Protocol: TrustedVolumes — Ethereum mainnet (1inch ecosystem liquidity provider/market maker)
1inch itself: Unaffected; 1inch clarified TrustedVolumes operates as an independent provider
Recovery: Stolen assets converted to ETH and distributed across multiple wallets; no recovery reported

Lessons for Auditors

Every external function that modifies a privilege set needs an access-control check. Functions that update allowlists, operator sets, or role mappings (addSigner, addOperator, setAdmin) must be gated by onlyOwner, an AccessControl role, a multi-sig, or time-locked governance. This is non-negotiable.
Enumerate all external/public write functions. RFQ, order-matching, and signature-scheme contracts often have auxiliary admin functions that auditors overlook. Systematically list every external and public non-view function and verify authorization for each.
Recurring attacker specialization. Linking the same behavioral fingerprint to the 2025 Fusion V1 exploit suggests a threat actor who specifically hunts RFQ and signature-scheme weaknesses. Protocols in this architecture class should pay extra attention to order-authorization paths.
Prefer immutable signer sets where possible. If the authorized signer set rarely changes, consider making it immutable at deployment or requiring a governance vote to update — eliminating the attack surface entirely.